The present invention relates to the field of surgical apparatus, and more specifically to tissue stabilizers such as may be used, for example, to perform cardiac surgery on a beating heart.
The growing interest in less invasive surgery has placed emphasis on cardiac surgery as well. The main difference in heart surgery with respect to other organ surgeries, gall bladder for instance, is that the beating motion of the heart tends to complicate the delicate surgical interventions that are normally performed in cardiac surgery.
Cardiac surgery has been traditionally performed with the support of a cardio-pulmonary machine, whereby the patient""s blood is oxygenated outside the body through extracorporeal circulation (ECC). This allows the surgeon to perform surgical procedures on a perfectly still heart, while the patient""s life support is maintained by cardiopulmonary assistance. During traditional coronary artery bypass graft (CABG) surgery, the surgeon or assistant may manually or otherwise manipulate the arrested heart into a position and orientation that yields the best access to a target coronary artery requiring a bypass graft, or coronary artery revascularization.
Recently, in an aim to render CABG surgery less invasive to the patient, beating heart CABG surgery is being developed whereby ECC, one of the most invasive aspects of cardiac surgery, is eliminated and coronary artery revascularization is performed directly on the beating heart. One of the challenges in performing beating heart CABG surgery lies in positioning and orienting the beating heart in order to obtain access to the inferior and posterior artery beds, while aiming to minimize physiologically undesirable effects such as hemodynamic instability, arrhythmia, or a precipitous drop in arterial pressure, that may occur as a result of such beating heart manipulation.
Another challenge lies in locally immobilizing at least a portion of the beating heart surface, or myocardium, in the vicinity of the target coronary artery requiring the bypass graft, or anastomosis, in an attempt to simulate the arrested myocardium normally operated on in traditional CABG surgery. To this end, a variety of movement restraining devices, or coronary stabilizers, have been and continue to be developed. Most coronary stabilizers have a contact member with a substantially planar body contact surface. The contact surface is typically interrupted by an opening, or arterial window, in the contact member in order to obtain access to the target artery exposed within the arterial window. The immobilization load applied by the coronary stabilizer to the heart tends to cause a protrusion or extrusion of myocardium tissue through the arterial window. The tissue extrusion obtained with a substantially planar contact surface applying a modest immobilization load on the heart, is generally quite small. Furthermore, with disposable-type plastic stabilizers, the contact member must be sufficiently thick to provide the required stiffness and rigidity in stabilizer design to adequately immobilize the contacted heart surface. As such, the generally small tissue extrusion through the arterial window may not even extend in height above the top, or exposed surface, of the relatively thick plastic contact member. In an attempt to improve the amount of tissue extrusion to a desired level in height, above the exposed surface of the contact member, a significantly greater immobilization load must be applied to the substantially planar contact member. As a result, this tends to impose restraints on the beating heart that may considerably impede its normal beating function, and induce the onset of the physiologically undesirable effects described above.
In light of foregoing, it would be beneficial to have a coronary stabilizer with an advantageously contoured body contact surface that tends to induce, entrain or promote a considerable extrusion of a portion of immobilized heart tissue through its arterial window. It would be a further advantage if this extrusion could be accomplished while at least a part of said contact surface also substantially conforms to the natural curvature of the heart. It would be yet a further advantage if this extrusion could be achieved with minimum impact to a heart chamber situated below the immobilized myocardium, thereby reducing the potential distortions in heart valvulature, and preserving hemodynamic stability.
In beating heart surgery, the pulsating effect of the heart may tend to induce disengagement or slipping of the contacted myocardium tissue relative to the contact surface of the coronary stabilizer. It would be beneficial to have a coronary stabilizer that has an advantageously contoured body contact surface, whereby this surface is configured with a tread or tissue-engaging texture that tends to enhance its traction on the contacted myocardium tissue.
Tissue stabilizers are typically manipulated through a handle that is connected to the body contact member. Tissue stabilizers may be kept in place by manually grasping and holding fixed said handle. Preferably, however, tissue stabilizers such as coronary stabilizers employed during a beating heart bypass surgery, are kept in place by securing said handle to a substantially stable surgical platform, such as a chest retractor. Said handle is usually engaged with a positioning means which is itself engaged to said retractor. Most coronary stabilizers have a handle extending away in height from the contact member, and from the contacted body tissue when in use. Such a handle may be referred to as a push-type handle because, in operation, said handle will tend to be in compression, when exerting a force against a portion of the heart, with its contact member. As such, surgical access to the arterial window, and to the exposed target coronary artery therein, may be compromised by the presence of said handle located generally within the surgical workspace situated above the arterial window. Based on the foregoing, and especially for posterior coronary artery revascularizations, it would be beneficial to provide a coronary stabilizer with an advantageously contoured contact member, and with a pull-type handle. Said pull-type handle extends away from the target artery in a direction that is generally rearwardly of the portion of heart tissue surface containing the target artery. This may tend to enhance the surgical access to the arterial window, by leaving the working access view of the arterial window unobstructed. It may also tend to permit a surgeon to obtain access to a lower side, or posterior portion of the heart. Finally, it may also help in maintaining the position of the beating heart in a substantially vertical orientation, with the apex directed generally outward of the retracted chest cavity, as may be required in order to access the posterior territory of the heart.
In beating heart CABG surgery, the heart continues to pump blood throughout the surgical procedure since ECC is avoided. As a result, an incision created in a coronary artery tends to cause bleeding within the surgical field. Surgical wires, preferably elastic vascular loops are sometimes used, during at least a part of the surgical procedure, to constrict or ligate a target coronary artery that will be surgically revascularized. A vascular loop is generally placed around a target coronary artery, at a location upstream of the intended arteriotomy and subsequent anastomosis, thereby serving to restrict blood flow through said target artery. Another such vascular loop may be placed at a location downstream of said arteriotomy incision, tending to minimize backflow from collateral arteries. As a result, an arteriotomy and subsequent anastomosis may be performed on said target artery in a substantially bloodless surgical field while the patient""s heart continues to beat. One such vascular loop, with integrally assembled tissue-piercing needle, is commercially available from Quest Medical, Inc. of Allen, Tex., under brand name xe2x80x9cRetract-O-Tape(trademark)xe2x80x9d.
Some coronary stabilizers are configured with anchoring features to secure said vascular loops. These anchoring features generally protrude above the heart contact surface of the coronary stabilizer, and as such, a vascular loop is generally secured to said stabilizer in a location situated in height above the heart contact surface of said stabilizer. Encircling of the target artery with a vascular loop, and subsequently pulling and securing the ends of said vascular loop to the coronary stabilizer, will tend to at least partially constrict the target artery. It may also tend to further extrude, through the arterial window, the portion of myocardium tissue containing the encircled target artery. This further extrusion is generally in addition to the extrusion that results when a coronary stabilizer with an advantageously contoured contact surface is engaged with a myocardium tissue. In light of the foregoing, it would be a further advantage if a coronary stabilizer with contoured contact surface is also provided with an array of surgical wire attachment fittings for engaging a surgical wire.
It is an object of the present invention to provide a tissue stabilizer, and more specifically a coronary stabilizer well-suited for performing beating heart CABG surgery, which tends to promote the extrusion of a contacted and substantially immobilized heart tissue, through an arterial window in said coronary stabilizer.
It is another object of the present invention to provide a coronary stabilizer with an advantageously contoured body contact surface, that tends to maximize the amount of tissue extrusion through an arterial window, when a given stabilization load is applied by said coronary stabilizer.
It is another object of the present invention to tend to improve surgical access to a coronary artery, especially a deep intramyocardial artery, by providing a coronary stabilizer which tends to extrude said artery through an arterial window in said coronary stabilizer.
These and other objects of the present invention will become apparent from the description of the present invention and its preferred embodiments which follows.